add SQL file and string test

Author: 0lai0

native/spark-expr/src/conversion_funcs/string.rs

@@ -1412,6 +1412,58 @@ mod tests {
         assert_eq!(ts_array.value(2), 1577836800000000);
     }
 
+    #[test]
+    #[cfg_attr(miri, ignore)]
+    fn test_cast_string_with_timezone_offset_to_timestamp_ntz() {
+        // Strings with explicit timezone offsets should produce null for TimestampNTZ
+        let array: ArrayRef = Arc::new(StringArray::from(vec![
+            Some("2020-01-01T12:34:56+05:00"),
+            Some("2020-01-01T12:34:56-08:00"),
+            Some("2020-01-01T12:34:56Z"),
+            Some("2020-01-01T12:34:56.123456+00:00"),
+            Some("2020-01-01T12:34:56.123456"),
+        ]));
+
+        let string_array = array
+            .as_any()
+            .downcast_ref::<GenericStringArray<i32>>()
+            .expect("Expected a string array");
+
+        let eval_mode = EvalMode::Legacy;
+        let result = cast_utf8_to_timestamp!(
+            &string_array,
+            eval_mode,
+            TimestampMicrosecondType,
+            timestamp_parser,
+            &Utc,
+            None::<&str>
+        );
+
+        assert_eq!(
+            result.data_type(),
+            &DataType::Timestamp(TimeUnit::Microsecond, None)
+        );
+        assert_eq!(result.len(), 5);
+
+        let ts_array = result
+            .as_any()
+            .downcast_ref::<PrimitiveArray<TimestampMicrosecondType>>()
+            .expect("Expected a timestamp array");
+
+        // All strings with timezone offsets should be null
+        assert!(ts_array.is_null(0), "'+05:00' offset should produce null");
+        assert!(ts_array.is_null(1), "'-08:00' offset should produce null");
+        assert!(ts_array.is_null(2), "'Z' suffix should produce null");
+        assert!(
+            ts_array.is_null(3),
+            "'+00:00' offset with micros should produce null"
+        );
+
+        // The one without offset should parse correctly
+        assert!(!ts_array.is_null(4));
+        assert_eq!(ts_array.value(4), 1577882096123456);
+    }
+
     #[test]
     fn test_cast_string_to_timestamp_ntz_via_cast_array() -> DataFusionResult<()> {
         let array: ArrayRef = Arc::new(StringArray::from(vec![

spark/src/test/resources/sql-tests/expressions/cast/cast_string_to_timestamp_ntz.sql

@@ -0,0 +1,39 @@
+-- Licensed to the Apache Software Foundation (ASF) under one
+-- or more contributor license agreements.  See the NOTICE file
+-- distributed with this work for additional information
+-- regarding copyright ownership.  The ASF licenses this file
+-- to you under the Apache License, Version 2.0 (the
+-- "License"); you may not use this file except in compliance
+-- with the License.  You may obtain a copy of the License at
+--
+--   http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing,
+-- software distributed under the License is distributed on an
+-- "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+-- KIND, either express or implied.  See the License for the
+-- specific language governing permissions and limitations
+-- under the License.
+
+-- ConfigMatrix: parquet.enable.dictionary=false,true
+
+-- Test casting string to timestamp_ntz
+-- https://github.com/apache/datafusion-comet/issues/3179
+
+statement
+CREATE TABLE test_cast_ts_ntz(s string) USING parquet
+
+statement
+INSERT INTO test_cast_ts_ntz VALUES ('2020-01-01T12:34:56.123456'), ('2020-01-01'), ('2020-01-01T12:34:56'), ('2020'), ('2020-01'), (NULL), ('not_a_timestamp'), ('2020-01-01T12:34:56+05:00')
+
+-- Cast string to timestamp_ntz: valid formats should parse, invalid should be null
+query
+SELECT s, cast(s AS timestamp_ntz) FROM test_cast_ts_ntz
+
+-- Verify that timestamp_ntz values are not affected by session timezone
+query
+SELECT s, cast(s AS timestamp_ntz) FROM test_cast_ts_ntz WHERE s = '2020-01-01T12:34:56.123456'
+
+-- Compare timestamp_ntz vs timestamp (with timezone) to show they differ
+query
+SELECT s, cast(s AS timestamp_ntz) as ts_ntz, cast(s AS timestamp) as ts FROM test_cast_ts_ntz WHERE s IS NOT NULL AND s != 'not_a_timestamp' AND s != '2020-01-01T12:34:56+05:00'